Chapter 2-Sec 3

& Chapter 3

Warm-up 2/14/13

Teach the Teacher: Valentines Day: love or hate and why?

Review: What is instantaneous speed?

What causes things to move the way they do?

ForcesForce—a push or pull that one body exerts on another

Balanced Forces Net Force—when 2 or

more forces act on an object at the same time

Balanced Forces—forces that are equal in size and opposite in direction.–An object will remain

still

Unbalanced Forces Unbalanced Forces—The size and

direction of forces acting on an object are unequal.–cause objects to move.

Balanced & Unbalanced Forces

Warm-up 2/15/13

Teach the Teacher: What was the hardest thing you have ever had to do?

Review: If I pull a bowl of macaroni and cheese across the room, is that a balanced force or unbalanced?

Flash Card

On the Front write:

Force

On the back write:

– is a push or a pull – can give energy to an

object causing motion

Inertia Inertia—the tendency of an object

to resist a change in its motion–Velocity of an object only changes if a

force changes it.

The inertia of an object is related to mass– The greater the mass, the greater its

inertia.

Newton’s 1st Law of Motion Newton’s 1st Law: The Law of

Inertia–An object at rest stays at rest and an

object in motion stays in motion with the same speed and direction unless acted on by an unbalanced force.

Warm-up 2/19/13

Teach the Teacher: How many presidents can you think of?

Review: How many different ways can you describe motion (think of the different triangles and graphs that we looked at)

Flash Card

On the front write:

Inertia

On the back write:

The resistance of an object to a change in its state of motion.

What Galileo did:

Galileo's Experiment

The ball would roll forever…..Like in space

Newton’s 1st Law of Motion

Punkin Chunkin: Inertia II

Punkin Chunkin: Inertia

http://www.youtube.com/watch?v=Xynn81pp9tg

Shooting Objects at RestThe object’s inertia causes it to remain still

even when a bullet passes through it.

Friction Friction: A force that opposes motion

between two surfaces that are touching each other

The amount of friction is dependant upon– Surfaces– Force pressing the surfaces together

Types of Friction Static Friction

– Friction between two objects that are NOT moving.

Sliding Friction– Friction between two surfaces moving past

each other. Rolling Friction

– Friction between a rolling object & the surface it is rolling on.

Fluid Friction – Friction between an object and a gas or liquid

Air Resistance Air Resistance: Collisions of the object's leading

surface with air molecules. Dependent upon a variety of factors, most

importantly– the speed of the object

Increased speeds = increased air resistance. – the cross-sectional area of the object

Increased cross-sectional area=increased air resistance

PTW:Air Resistance Challenge Put your name on both sheets of paper One sheet=design a “papercraft” that will

have A LOT of air resistance Other sheet=design a “papercraft” that will

have VERY LITTLE air resistance WHEN DROPPED FROM THE SECOND

STORY BALCONY YOU WILL FAIL IF YOU DON’T PICK IT

UP!

PTW: Air Resistance Challenge

1. Why did your A LOT of air resistance design work or not work?

2. Why did your VERY LITTLE air resistance design work or not work?

3. What would make a sky diver slow down? What would make them speed up?

Warm-up 2/20/13

Teach the Teacher: What is the best kind of fruit?

Review: What has more inertia, string cheese or a puppy?

NO LIQUIDS OR GELS (INCLUDING PEANUTBUTTER) or ANYTHING STICKY for EGG DROP!

Flash Card

On the front write:

Newton’s First Law

On the back write:

Objects at rest stay at rest….

Objects in motion stay in motion…. unless acted on by another force

PTW: Keep the Change http://www.nbc.com/minute-to-win-it/how-to/

keep-the-change/ The Challenge: Design an inertia

demonstration and present why it demonstrates inertia/Newton’s first law.

PTW: Keep The Change

Jobs: Recorder, Presenter 1, 2, 3 (some people might have to do more then one)

1. What is inertia? What is Newton’s First Law

2.What did you do to demonstrate inertia/Newton’s first law?

3. How does the demonstration show inertia/Newton’s first law?

Warm-up 2/21/13

Teach the Teacher: When is a time that you have laughed at yourself?

Review: What kind of speed is measured from a total distance divided by the total time?

Flash Card

On the Front:

Balanced Forces

On the Back:

Forces that are equal in opposite directions = no movement

Flash Card

Front:

Unbalanced Forces

On the Back:

One force being larger than the other in opposite directions = movement

Newton’s Second Law Newton’s 2nd Law: The acceleration of an object is

dependent upon the force acting upon the object and the mass of the object.

Newton’s Second Law as an equation: F = m × a    F = force (N)  Newton is the SI Unit of force m = mass (kg)    N = kg m / s2

a = acceleration (m/s/s)

Units

The SI unit for mass =kilogram (kg) The unit for acceleration = meters

per second squared (m/s2) So the unit for force = kg x m/s2

The kg x m/s2 is called the newton (N)

Tugboat Problems Two tugboats are moving a barge.

Tugboat A exerts a force of 3000 Newtons on the barge. Tugboat B exerts a force of 5000 Newtons in the same direction. What is the combined force on the barge? Draw arrows showing the individual and combined forces of the tugboats.

Tug Boat Questions

Now suppose that Tugboat C exerts a force of 2000 Newtons on the barge and Tugboat D exerts a force of 4000 Newtons in the opposite direction. What is the combined force on the barge? Draw arrows showing the individual and combined forces of the tugboats.

Warm-up 2/22/13

Teach the Teacher: What will be the best thing about being an adult that has graduated from high school?

Review: What kind of friction is caused by socks rubbing on the carpet?

Flash Card

On the front write:

Air resistance

On the back write:

A force on objects as they fall through the air.

Flash Card

On the front write:

Newton’s 2nd law

On the back write:

Acceleration of an object depends on the mass and force

F=ma

Warm-up 2/25/13

Teach the Teacher: Do you think you will be a parent some day? If so, how do you want to be like your parents/guardians?

Review: What is the force that is caused by air pushing up on an object as it falls?

Flash Card

On the front write:

Mass

On the back write:

The amount of matter in an object, doesn’t change (units=g and kg)

Warm-up 2/26/13

Teach the teacher: What is the “secret ingredient” for an egg drop container?

Review: What is the units for force?

Warm-up 2/27/12

Teach the Teacher: If you could break the world record in something, what would you want to break it in?

Review: What is the unit for acceleration?

Flash Card

On the front write:

Gravity

On the back write:

An attractive force between two objects depend on the mass and distance

Gravity Universal law of Gravity:

– Any 2 objects will exert an attractive force on each other

– The size of the force is dependant on 2 things Mass of both objects Distance between the objects

– The range of gravity never disappears Therefore it is not possible for an

object with mass to be weightless.

Weight vs. Mass Weight: Force of gravity pulling you toward the earth

– F = ma becomes W = mg – Weight = mass × gravitational acceleration

g on Earth is 9.8m/s2

– SI Unit = Newton– Weight can change with a change in location.

Mass: A measure of how much matter an object has– You know an object has mass because

it has inertia– SI Unit = Kilograms

Centripetal Force Centripetal Force: The force exerted

toward the center of a curved path. Earth’s gravity exerts a centripetal force

on the Moon that keeps it in a nearly circular orbit.

Real World/space station & centripetal force

Roller coaster Loops

Warm-up 2/28/13

Teach the Teacher: Would you rather eat worms or mold?

Review: What is the circular force called when something spins in a circle?

Flash Card

On the front write:

Weight

On the back write:

The force of gravity pulling on you, changes in the universe

How to Do Space Weight

The last questions

Falling Objects on Earth Near Earth’s surface

acceleration due to gravity is 9.8 m/s2

If 2 objects with different masses are dropped from the same height, which would hit the ground first?

http://www.youtube.com/watch?v=aRhkQTQxm4w&feature=plcp

dropping objects on the moon

Projectile Motion Anything dropped, thrown, or shot through the air

is a projectile Because of gravity and inertia, you can get a

curved path.

http://video.pbs.org/video/1602463762/

http://science360.gov/obj/tkn-video/fc729ef0-22ee-4f61-bb2a-b6c07685fb02/science-nfl-football-projectile-motion-parabolas

Monkey and the Zookeeper The zookeeper must shoot the

banana from the banana cannon to the monkey who hangs from the limb of a tree.

This particular monkey has a habit of dropping from the tree the moment that the banana leaves the muzzle of the cannon.

The zookeeper is faced with the dilemma of where to aim the banana cannon in order to hit the monkey.

If the monkey lets go of the tree the moment that the banana is fired, then where should she aim the banana cannon?

Monkey and the ZookeeperWhere should the zookeeper aim?Taking Gravity into effect The zookeeper aims above the monkeyDoes the speed of the banana change the effect?The zookeeper aims at the monkey and shoots the banana very fast The zookeeper aims at the monkey, yet shoots the banana very slow. ZOO in SPACEIn a low gravity environment, where should the zookeeper shoot the banana?

Physics To Win It

Hole in One Challenge: To roll a golf ball off the ramp, off

the table, and land in the cup…I have to see it.

Jackpot challenge: To get a golf ball to do the above, bounce once and land in the cup

On an index card calculate the velocity of the ball

NEWTON’S 3rd LAW:

For every action, there is an equal and opposite reaction

“Action” and “Reaction” are names of forces

Forces ALWAYS occur in pairs Single forces NEVER happen

“Equal & Opposite” In Newton’s 3rd Law,

“equal” means: Equal in size Equal in time.

– occur at EXACTLY the same time.

In Newton’s 3rd Law, “opposite” means:

Opposite in direction– forces are EXACTLY

180o apart in direction.

Only forces that act on the same object can cancel.

Newton’s 3rd Law action and reaction forces act on different objects, so they DON’T cancel.

Writing Action Reaction Forces–ACTION

Bowling ball hits the pin to the left.

–REACTION

Pin hits the bowling ball to the right

Momentum: A property of how much force is required

to change the object’s motion – The object’s mass times its velocity

p = mv– p = momentum– m = mass– v = velocity

SI UNIT = Kg m / s

Law of Conservation of Momentum Momentum may be

transferred to another object

The total momentum before a collision is equal to the total momentum after the collision

m1v1 = m2v2

Physics To Win it Challenge

Back Flip

1.Draw a diagram of the forces working on your hand and pencil BEFORE the flip

2. Draw a diagram of a the forces working on your hand and pencil DURING the flip

Types of Collisions Elastic collisions

– the total kinetic energy before the collision is equal to the total kinetic energy after the collision.

– Usually the objects bounce off of each other.

Inelastic collisions– the total kinetic energy before the collision is NOT

equal to the total kinetic energy after the collision.– Usually the objects stick together

interactive

The Truck and The Ball A pickup truck is moving with a constant speed. In the course of its motion, a ball is projected straight

upwards by a launcher located in the bed of the truck. Assume the ball does not encounter a significant amount

of air resistance. What will be the path of the ball and where will it be

located with respect to the pickup truck?

Many would insist that there is a horizontal force acting upon the ball since it has a horizontal motion.

Yet this is simply not the case. The horizontal motion of the ball is the result of its own inertia.

When projected from the truck, the ball already possessed a horizontal motion, and thus will maintain this state of horizontal motion unless acted upon by a horizontal force.

An object in motion will continue in motion with the same speed and in the same direction ... (Newton's first law).

Newton's Law Review physclips newton's laws http://www.phys.unsw.edu.au/einsteinlight/